Protein synthesis ceases in the red cells at the reticulocyte stage. Hence, a progressive decline in metabolic capacities of the red cells continues until a level is reached incompatible with cell survival. The biochemical changes that accompany aging of the red cell will be evaluated by studying groups of cells of progressively increasing age separated by density gradient ultracentrifugation. Metabolic parameters that will be thus evaluated will include enzymatic activities, accumulation of intermediates, changes in kinetic behavior of enzymes of key metabolic importance. The use of density gradients on arabino-galactane for preparation of cell fractions in quantities eventually applicable to clinical transfusion will be evaluated. These studies will be directed at the preparation of red cell fractions with improved survival and of platelet concentrates with complete yield, including the heaviest and most functional ones. The isozymes of phosphofructokinase will be studied in normal human blood as well as in blood of individuals genetically defective for this enzyme. As a sideline of this study, patients with Cooley's Anemia will be maintained at a Hgb level as nearly normal as practicable. The reasons for this treatment have been detailed to the patients' parents and informed consent is obtained before each transfusion and admission. BIBLIOGRAPHIC REFERENCES: Piomelli, S., Brickman, A., Carlos, E.: Rapid Diagnosis of Fe Deficiency by Measurement of Free Erythrocyte Porphyrins (FEP) and Hemoglobin: The FEP/Hemoglobin Ratio. Pediatrics 57: 136-141, 1976. Piomelli, S., Corash, L.M.: Hemolytic Anemia Due to Enzyme Defects of Glycolysis. Adv. Hum. Genet., (Eds.) Harris, H. and Hirschhorn, K., 6: 165-240, 1976.